Clams are animals that burrow under the sea floor. They are bivalves, mollusks that have two shells that protect a soft body. There are over 15,000 different species of clams worldwide. The biggest clam is the Giant Clam, Tridacna gigas; it is up to 4.8 feet (1.5 m) long and weighs up to 550 pounds (250 kg). Most clams are only a few inches long.

Anatomy and Diet: Clams come in many colors, including shades of brown, red-brown, yellow, cream, etc. The two shells are attached by a muscular hinge (the adductor muscle). When a clam is threatened, most clams will pull their soft body into into the shells and close the shells tightly for protection. The foot is used to burrow into the sand. Clams use their tube-like siphon to draw in water, from which they extract oxygen and filter plankton (tiny plants that they eat).